Conventionally, there has been known the 3GPP GPRS network, which is an example of a mobile communication network (mobile network) provided with multiple gateways (hereinafter referred to as GWs) (see “FIG. 64: PDP Context Activation Procedure for Iu mode” of Non-Patent Document 1, for example).
As shown in FIG. 1, in the GPRS network, when a communication starts, a mobile terminal MS notifies an exchange SGSN (serving GPRS support node) of an “access point name (APN)” indicating a connection destination network, by using a message 1.
Accordingly, by inquiring of a GW solution device such as a DNS (domain name server), the exchange SGSN identifies an exchange GGSN (gateway GPRS support node) that is a gateway.
Then, the exchange SGSN sets up a route to the exchange (gateway) GGSN through exchange of messages 4 and 9.
In a handover preparation procedure for a case where the mobile terminal MS moves across the exchanges SGSN during a communication, the exchange SGSN before the handover (former SGSN) notifies the exchange SGSN after the handover (new SGSN) of context information (including GGSN information) on the mobile terminal MS, by using a message 3, as shown in FIG. 2.
Accordingly, the exchange SGSN after the handover (new SGSN) becomes able to uniquely identify the exchange GGSN used before the handover by the mobile terminal MS, and thus to set up a route to the exchange GGSN by exchanging messages 13.
As a result, even after the handover of the mobile terminal MS, a mobility service can be provided to the mobile terminal MS by utilizing the same exchange GGSN (See “FIG. 42: Combined Hard Handover and SRNS Relocation Procedure” of Non-Patent Document 1).
The mobile communication network described above is based on the assumption that before and after the handover, the context information on the mobile terminal can be transferred between the access devices (the exchanges SGSN in the above example) that perform a process of changing a routing path in the network in response to movement of the mobile terminal.
That is, during a handover, using a function to transfer the context information allows the access devices to share information on GW (the exchange GGSN in the above example) used by the mobile terminal MS. Thus, the same gateway can be selected before and after the handover.
Non-Patent Document 1: “General Packet Radio Service (GPRS): Service description: Stage 2”, 3GPP TS23.060 V7.2.0, September 2006
Non-Patent Document 2: “3GPP System Architecture Evolution: Report on Technical Options and Conclusions”, 3GPP TR23.882 V 1.4.0, September 2006
Non-Patent Document 3: “Numbering, addressing and identification”, 3GPP TS23.003 V7.1.0, September 2006